A related-art disk motor mainly includes an output shaft, a coil disk fixed to the output shaft, having substantially a circular plate shape and on which a coil pattern is printed, a commutator connected to the coil pattern, a magnet disposed so as to face the coil pattern, and a brush for supplying current to the commutator (see JP-A-2003-299288).
A number of rotations of the disk motor is determined by a voltage supplied from the brush, a current of the disk motor, the coil pattern of the coil disk, a magnetic flux of the magnet, the number of brushes (the number of poles), etc. When the voltage supplied from the brush and the current of the disk motor are constant, the disk motor can be set at a desired number of rotations by changing the coil pattern of the coil disk, the magnetic flux of the magnet or the number of brushes.